The condensation polymerization of silphenylene diol with disiloxanol fluids in the presence of a condensation catalyst and a solvent, is described in U.S. Pat. No. 3,202,634 incorporated herein by reference and is shown generally in the equation below: ##STR1## where x is equal to 30-35, y is equal to 9-12, and z is equal to 30-40.
The polymerization yields a high molecular weight semi-crystalline block copolymer, the melting point (Tm) of which is dependent upon the mole fraction of (Me.sub.2 SiO) and the degree of randomness. Water formed during polymerization is removed azeotropically to permit a build-up in viscosity as polymer chains lengthen. The preferred polymerization catalysts are amine salts, and the resultant polymers are soluble in halogenated solvents.
In the foregoing polymerization, a combination of high molecular weight and high crystalline melt temperatures of the copolymer of greater than 90.degree. C. causes isolation problems when the reaction is carried out in standard polymerization vessels. The copolymer must either be dissolved while in the polymerization vessel in a suitable solvent and discharged as a liquid solution, for example, a 35 percent solution of the silarylenesiloxane copolymer in methylene chloride, or the copolymer can be discharged from the polymerization vessel while hot and in the molten state, for example, through a ribbon extruder.
In order to facilitate handling and compounding of the curable polymeric compositions, these compositions should preferably be in a low density, dry, granular, free-flowing form which facilitates handling, bulk loading, shipping and mixing or compounding. Granular compositions of uniform density are desirable for accurate metering and transfer to extrusion or injection molding machinery.
In the prior art, these block copolymers after polymerization in the polymerization vessel were either redissolved in a suitable solvent, for example, methylene chloride, discharged as a solvent solution then reprecipitated in alcohol to give a granular product, or, alternatively, the polymer from the polymerization vessel is melted or maintained in a molten state and discharged hot, for example, through a ribbon extruder at high temperature, then cooled, for example, in a trough of water to form sheets or strips of the curable polymer. These sheets or strips were then cut or diced to a particle size which facilitates operations such as shipping and handling and made possible efficient compounding or blending of the copolymer with fillers, extenders or coagents in extrusion or injection molding machinery. Both of these methods have serious shortcomings. The redissolution and precipitation method requires, for each pound of curable polymer, approximately three pounds of solvent to dissolve the polymer, and an additional 10 pounds of alcohol to precipitate the dissolved polymer. This process involves relatively high isolation costs including solvent recovery and the cost of unrecoverable solvent.
The method involving cutting or dicing the sheets or strips of the curable polymer is rate limited by the possibility of melting the polymer on the cutting blades due to the heat generated by shear in the cutting operation.
The above-mentioned methods are costly in terms of both time, labor, solvent recovery and solvent loss.